Tuesday, as those who follow politics probably know, is Election Day. The battle between President Barack Obama and Republican challenger Mitt Romney has been contentious, expensive, personal, illuminating, ugly, frustrating, petty, enlightening and, above all, long. And it is expected to be close.

This week's Political Junkie column is an attempt to guide you to what's at stake on Tuesday, both in the contest for the White House as well as the 33 Senate and 435 House seats on the ballot.

And please be sure to tune in to NPR's live election night coverage, beginning at 8 p.m. Eastern time Tuesday night. We're scheduled to be on the air until 3 a.m. Wednesday morning, longer if we don't have a presidential winner.

President. Every vote counts, we hear over and over again. In a close election — as Tuesday's presidential contest is expected to be — you'll be constantly reminded of the importance of casting your ballot.

But some votes count more than others. Yes, voters in 50 states and the District of Columbia will be going to the polls. But since so many of the states are already "decided" in the minds of the candidates and voters — states like California and New York and Texas and Illinois, where the race for president is not considered to be in doubt — the election will be decided in what is commonly called "battleground" states, the seven or eight states that presumably are too close to call.

They are, in terms of electoral clout, Florida (with 29 electoral votes), Ohio (18), Virginia (13), Wisconsin (10), Colorado (9), Iowa (6) and New Hampshire (4). Democrats have been talking hopefully about North Carolina (15), but by most accounts Romney may have the edge there. Similarly, the Romney campaign has been talking about, and spending money in, states like Michigan (16) and Pennsylvania (20) in recent days. We don't know if they see a real opportunity there, are bluffing, or need to have a contingency plan if, say, Ohio is out of reach. But both are considered leaning Democratic.

The fact of the matter is, every state listed above all went for Obama in 2008. No state that was carried by John McCain is thought to be at risk for the Republicans. So the battleground will be in these seven states.

Third parties. As is usually the case, the candidates representing minor parties are not expected to get any significant vote. The Libertarian Party, for example, is usually on the ballot in more states than any other third party. But the most votes a Libertarian presidential candidate ever received was the 921,299 (1.1 percent) won by Ed Clark in 1980. Gary Johnson, the former Republican governor of New Mexico, is this year's Libertarian Party candidate. He's on the ballot in 48 states. He is followed by Jill Stein, the Green Party candidate, on the ballot in 38 states. Virgil Goode Jr., the former Democratic-turned-Independent-turned-Republican congressman from Virginia, is on 25 state ballots as the Constitution Party candidate. Of course, the one state to watch for any meaningful Goode vote is his home state of Virginia, where Obama and Romney are basically tied. He doesn't have to get much of a vote to make a difference. Remember 2000? Green Party nominee Ralph Naderonly received 1.7 percent of the vote in Florida, one of his weakest showings of any state he appeared on the ballot that year. But that 1.7 percent translated into some 97,000 votes, which many Democrats insist cost Al Gore the state — and the presidency.

Among the other third party candidates this year include the actress Roseanne Barr, in five states as the Peace & Freedom Party nominee, and the Socialist Workers Party'sJames Harris, in six states.

Senate. Democrats, including two independents who vote with them, have a 53-47 majority. Of the 33 seats up for grabs Tuesday, 23 are held by the Democrats. Republicans need to have a net pickup of three seats, if Romney is elected, to win a Senate majority, four if Obama wins. The GOP is hoping to make gains in states being vacated by retiring Democrats, such as Wisconsin (where Herb Kohl is leaving), North Dakota (Kent Conrad), Nebraska (Ben Nelson) and Virginia (Jim Webb). But they are also hurt by Olympia Snowe'sretirement in Maine and Dick Lugar's primary defeat in Indiana. Other Republican-held seats to watch are in Massachusetts, Arizona and Nevada. Democrats are worried about Sen. Jon Tester in Montana.

Women. There are a record number of female candidates for Congress this year, including 18 for the Senate. Two women — Kay Bailey Hutchison of Texas and the aforementioned Snowe of Maine — are leaving. But there's a guaranteed additional woman in Hawaii (where Democrat Mazie Hirono faces Republican Linda Lingle), and women are at least even money to win in Massachusetts and Nebraska. Plus, there are strong female candidates in Connecticut, Nevada, North Dakota and Wisconsin. If Tammy Baldwin (D) wins in Wisconsin, she would be the first openly gay or lesbian candidate ever elected to the Senate.

Independents. There are currently two in the Senate. One, Bernie Sanders of Vermont, is all but assured of re-election. The other, Joe Lieberman of Connecticut, is retiring. Angus King, the former two-term independent governor of Maine, is favored in his own indie bid for an open Senate seat. Like Sanders and Lieberman, he is expected to vote to organize the Senate with the Democrats. And while Sen. Ben Cardin (D) is a clear favorite for a second term in Maryland, there is a possibility that a free-spending independent could outpoll the GOP nominee for second place.

House. We have had three successive "wave" elections in the House: 2006, when the Democrats picked up 31 seats and made Nancy Pelosi speaker; 2008, when the Dems extended their lead with 20 more seats; and 2010, when Republicans had a net gain of 63 seats. Right now, if you apportion the current vacancies to their former parties, Republicans have a 242-193 majority in the House. Thus, Democrats need a net gain of 25 seats.

Some notable "characters", such as Barney Frank (D-Mass.), Dennis Kucinich (D-Ohio) and Ron Paul (R-Texas), won't be returning. But a Kennedy — Joe Kennedy III (D-Mass.), RFK's grandson — will be in Congress after a two-year absence. And there are some other things to watch as well. Mia Love, who is challenging Rep. Jim Matheson (D) in Utah, could become the nation's first African-American female Republican elected to the House (and in Utah of all places). If Republicans take the Arkansas seat that Democrat Mike Ross is vacating, it would be the first time the GOP won every House seat in the state's delegation. If Democrats defeat Frank Guinta and Charlie Bass — the two Republican House members from New Hampshire — it would be the first time in history women will have every congressional seat in a state's delegation; Kelly Ayotte (R) and Jeanne Shaheen (D) are already in the Senate. (And another woman, Maggie Hassan, is running for governor.)

Other potential milestones: Rep. John Barrow (D-Ga.), the last remaining white Democratic House member from the Deep South, is in a tight race for re-election. Massachusetts, which hasn't elected a Republican to its House delegation since 1994, could elect one in the 6th District, where Democratic incumbent John Tierney has ethics problems and the GOP is running Rich Tisei, an openly gay pro-choice candidate. And for the first time in 80 years, a House member — in this case, Wisconsin's Paul Ryan — is running for both vice president and re-election to his congressional seat.

Governors. Just 11 gubernatorial contests on the ballot this year. The best chance for a change in party comes in North Carolina, where Gov. Bev Perdue (D) is retiring after one term and the GOP leads in the polls. Three other states where Democratic incumbents are leaving — Montana, Washington and New Hampshire — are close.

Ballot initiatives. All eyes are on same-sex marriage questions in Maine, Maryland and Washington. No state has yet to approve gay marriage legislation via popular vote; the ones that have such a law on the books got there either by state legislature or judicial action.

PREDICTIONS:

President. Obama wins a second term, getting 277 electoral votes to Romney's 261. The swing states of Iowa, Nevada and Ohio go to Obama. Colorado, Florida, New Hampshire and Virginia go Romney.

House. Little change. Whichever party picks up seats, it should be in single digits. And it's not out of the question for Republicans to wind up with, say, plus-two seats.

So, Obama wins, Democrats keep the Senate, Republicans keep the House. Which is exactly where we were when this whole thing started.

ELECTION NIGHT TICK-TOCK (focusing on key states only; poll closing times all Eastern):

7 p.m.: Polls in Indiana and Virginia close. If Richard Mourdock (R) loses in Indiana, you can kiss the GOP's hopes of winning a majority in the Senate goodbye. Hard to imagine Romney winning the White House without Virginia; if he loses, watch to see if third party Goode is the difference.

7:30 p.m.: All eyes on Ohio. Both Obama and Romney could win the White House without this state, but it would be tougher for Romney. He needs North Carolina as well, where Republicans have opportunities for gains in the House.

8 p.m.: Key states are Florida and New Hampshire. Romney cannot win the presidency without the Sunshine State, and he needs N.H. too. House races to watch in both states, as well as Illinois, which could be the Dems' best House opportunity. We'll see if the GOP's courting of Pennsylvania was for real. Big Senate seats in Massachusetts and Missouri, but Connecticut bears watching as well.

9 p.m.: Colorado is the key presidential state. The rest are mostly about Senate races in Arizona, Nebraska, North Dakota and Wisconsin.

10 p.m.: Iowa and Nevada are the last presidential swing states to watch. Big Senate races in Nevada and Montana.

11 p.m.: After California polls close, we should get a better picture about the battle for the House.

Political Updates. I post periodic political updates during the week — some serious, some not — on Twitter. You can follow me at @kenrudin. Here's one e-mail that I'd like to share. It comes from Jeff Rosenberg, a retired NPR producer and manager now working on an assignment in Berlin:

"So, I'm in Berlin this week working on a project, and tonight I had dinner with a number of Americans and their spouses, some of them Germans. The talked turned quite naturally to the coming elections.

One 30-ish young man, Daniel Cukierman, was actually born and raised in West Berlin, but went to college in the USA and became a big NPR fan. He told me he is completely hooked on NPR's political coverage, and he is actually "the listener" to your It's All Politics podcast. He claims he NEVER misses it and hates it when you take a week off.

He told me that he listens in the bathroom on Friday mornings as he's getting ready to go to work. He turns it up pretty loud so he can hear it over running water, etc. He has an iPod dock with speakers, and it can easily be heard throughout their apartment.

This has been going on regularly for ages. He and his wife have a young son and a nanny to help care for him. She would hear the noises in the bathroom on Friday mornings, especially Daniel's laughter and she became very curious. One morning, she asked Daniel's wife, "Why does your husband always have a conference call so early in the morning on Friday? He must be very important."

I couldn't make this up."

Political Junkie segment on Talk of the Nation. Each Wednesday at 2 p.m. ET, the Political Junkie segment appears on Talk of the Nation (NPR's call-in program), hosted by Neal Conan with me adding color commentary, where you can, sometimes, hear interesting conversation, useless trivia questions and sparkling jokes. Last week's show was devoted to a full hour of looking ahead to Tuesday's elections. Special guests: Democratic pollster Anna Greenberg and Republican journalist Matthew Continetti. You can listen to the segment here.

This Wednesday we'll be on for a full TWO HOURS (2-4 p.m.), with full analysis of the election results.

But, before that, make sure you tune into NPR's election night coverage, starting at 8 pm Eastern and scheduled to go — at least — until 3 a.m.

Podcast. There's also a new episode of our weekly podcast, "It's All Politics," up every Thursday. It's hosted by my partner in crime, Ron Elving, and me.

And Don't Forget ScuttleButton. ScuttleButton, America's favorite waste-of-time button puzzle, can usually be found in this spot every Monday or Tuesday. A randomly selected winner will be announced every Wednesday during the Political Junkie segment on NPR's Talk of the Nation. You still have time to submit your answer to last week's contest, which you can see here. Not only is there incredible joy in deciphering the answer, but the winner gets not only a TOTN tee-shirt, but a 3-1/2-inch Official No-Prize Button!

Last week's winner: Ingvild Stub of Chevy Chase, Md.

Mailing list. To receive a weekly email alert about the new column and ScuttleButton puzzle, contact me at politicaljunkie@npr.org.

******* Don't Forget: If you are sending in a question to be used in this column, please include your city and state. *********

This day in campaign history: Richard Nixon is elected the 37th President of the United States. Nixon, who as vice president lost the 1960 presidential election to John F. Kennedy and then two years later was defeated in his bid to become governor of California, narrowly beats Vice President Hubert Humphrey, 43.4 percent to 42.7 percent — a difference of just 510,000 votes. But it's not close in the Electoral College: 301 to 191, with 46 going to an independent candidate, former Alabama Gov. George Wallace. Democrats, as expected, retain control of the House and Senate (Nov. 5, 1968).